Retinol (vitamin A) is an endogenous compound which occurs naturally in the human body and is essential for normal epithelial cell differentiation. Natural and synthetic vitamin A derivatives have extensively been used in the treatment of a variety of skin disorders and have been used as skin repair or renewal agents. Retinoic acid has been employed to treat a variety of skin conditions, e.g., acne, wrinkles, psoriasis, age spots and discoloration. See e.g., Vahlquist, A. et al., J. Invest. Dermatol., Vol. 94, Holland D. B. and Cunliffe, W. J. (1990), pp. 496-498; Ellis, C. N. et al., "Pharmacology of Retinols in Skin", Vasel, Karger, Vol. 3, (1989), pp. 249-252; Lowe, N. J. et al., "Pharmacology of Retinols in Skin", Vol. 3, (1989), pp. 240-248; PCT Patent Application No. WO 93/19743. Retinol and retinyl esters, such as retinyl acetate and retinyl palmitate, are easier to formulate/stabilize than retinoic acid. Unfortunately, retinol and retinyl esters are less effective than retinoic acid at providing skin benefits. The present invention is based, in part, on the discovery that certain combinations of retinol or retinyl esters with dimethyl imidazolidinone result in a synergistic improvement in keratinocyte proliferation and differentiation. The effects of dimethyl imidazolidinone combined with retinol or a retinyl ester were analogous to the effects of retinoic acid. Thus, a mixture of fatty acid amides with retinol or retinyl esters mimics retinoic acid yet is easier to use than retinoic acid.
Dimethyl imidazolidinone is currently used in cosmetic products to combat bacterial contamination. The art does not disclose, however, skin conditioning compositions based on synergistic combinations of dimethyl imidazolidinone with retinol or a retinyl ester. None of the art cited above addresses the need for an effective alternative to retinoic acid.
Accordingly, it is an object of the present invention to provide a skin conditioning composition containing a combination of retinol or a retinyl ester with dimethyl imidazolidinone.
It is another object of the invention to provide a method of conditioning skin with a composition containing as an active system a mixture of dimethyl imidazolidinone with retinol or a retinyl ester.
It is yet another object of the invention to provide a substitute for retinoic acid in cosmetic compositions.
These and other objects of the invention will become more apparent from the detailed description and examples that follow.